To reduce a leakage amount of working fluid flowing from a high-pressure side to a low-pressure side, a shaft sealing apparatus is installed around a rotor in a rotating machine such as a gas turbine or a steam turbine. As an example of the shaft sealing apparatus, for example, the shaft sealing apparatus disclosed in Patent Document 1 below is known.
Such a shaft sealing apparatus is equipped with a housing installed on a stator, and a seal body made up of numerous thin seal pieces.
The seal body is configured so that the numerous thin seal pieces are mutually stacked with microgaps with a thickness direction of each thin seal piece directed in a circumferential direction of a rotor. Every thin seal piece is slantingly disposed so that a radial inner end (front end) thereof is located at a position closer to a rotating-direction front side of the rotor than a radial outer end (rear end) thereof. The thin seal pieces are configured so that the rear ends thereof are connected to one another, and so that the front ends thereof are free ends.
In the shaft sealing apparatus schematically configured in this way, when the rotor stands still, the front end of each thin seal piece is in contact with the rotor. In contrast, when the rotor rotates, the front end of each thin seal piece is raised from an outer circumference of the rotor and comes out of contact with the rotor due to a dynamic pressure effect caused by the rotation of the rotor. For this reason, in the shaft sealing apparatus, the wear of each thin seal piece is suppressed, and a seal service time is increased.
FIG. 11 is a schematic configuration view of a conventional shaft sealing apparatus 110. The shaft sealing apparatus 110 is configured so that a plurality of seal segments 111 extending in a circular arc shape are disposed in a toric housing 9 supported on an inner circumferential surface of a stator.
The seal segment 111 is made up of a seal body 112 composed of numerous thin seal pieces 120, holding rings 113 and 114 having a U-shaped cross section and holding the numerous thin seal pieces 120, and high-pressure side lateral plate 116 and low-pressure side lateral plate 117 installed with the seal body 112 interposed therebetween in an axial direction of the rotor.
The holding rings 113 and 114 are members for holding head parts 121 of the numerous thin seal pieces 120. Further, rotor radial outer ends of the high-pressure side lateral plate 116 and low-pressure side lateral plate 117 are formed with protrusion parts 116a and 117a directed in the axial direction. The protrusion parts 116a and 117a are held so as to be prevented from falling off in a radial direction by the holding rings 113 and 114 in a state in which they are inserted into dents 123 between the head parts 121 and body parts 122 of the thin seal pieces 120.